The overall objective of this research program is to understand the role of limited proteolysis in physiological processes. On the biological level we wish to define the variety of processes that are regulated by limited proteolysis of protein precursors; on the molecular level, we wish to elucidate the chemical changes responsible for the attendant biological response. We also wish to exploit limited proteolysis in the strategy of protein sequence analysis. Our research goal during the next year includes the following projects: 1. A study of the limited proteolysis of citrate synthase, preliminary to the complete sequence analysis of this enzyme. 2. A study of the structure and function of a mast cell protease. 3. Search for the occurrence of a zymogen form of enterokinase and partial sequence analysis of the enzyme by semimicro sequencing techniques. 4. A study of the mechanism of transmembrane secretion and characterization of the "signal peptidase". 5. Structure and physiological role of an acrosin-like enzyme of sea urchin sperm. 6. Sequence analysis of protein kinase, crayfish protease, pig heart citrate synthase, and determination of disulfide pairing in blood coagulation factors IX and X.